Method and apparatus for making composite strip stock



ugz 5; E946@ c. A; MANN 29459222 METHOD AND APPARATUS -FOR MKINGCOMPOSITE STRIP STOCK Filed Nov. 5m 1944 v Patented Aug. 6, 1946 UNiTEDST METHOD AND APPARATUS FOR MAKING COMPOSITE STRIP STOCK Cecil A. Mann,Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., acorporation of Delaware Application November 30, 1944, Serial No.565,977

.3 Claims. 1

This invention relates to iluxing equipment for metal strips and isparticularly concerned with llXiIlg equipment used in connection withelectrical heating of the strips and to the method of uxing said strips.i

This application is a continuation in part of my copending application,Serial No. 376,512. In said copending application, a method andapparatus for electrically heating a metal strip is shown wherein thesurface of the strip is conditioned for subsequent babbitting operationsthereon.

This invention is particularly directed to the resistance heating of theelectrical strip where.. in the molten babbitt to 'be placed on thesurface of the strip is used as one electrode for the current whichpasses through the strip during the resistance heating thereof. In theapparatus shown in my copending application, it has been found thatunder certain conditions, difficulty is experienced in that the backsideof the strip, a1- though not conditioned for babbitting,' will sometimespick up babbitt when heated by resistance. This phenomena while onlyoccasional, necessitates removal of the babbitt from the backside of thestrip and therefore is objectionable 'when it occurs. The explanationfor the phenomena -is one which is difficult to expound but is probablydue to the fact that the current passes through the babbitt and into thestrip in sucient quantity to overheat the strip on the backside thereofat the instant it enters the babbitt chamber or stated differently,there is a potential difference at the opposite sides of the strip.

It is, therefore, the prime object of this invention to provide anapparatus and a method for passing current into the strip from thebabbitt so that the strip is heated uniformly and so that theconditioning thereof is apparent only on one side thereof.

In carrying out the above object it is a further object to provide anapparatus -wherein molten babbitt is present on the top side of thestrip prior to the time the -bottom side of the strip contacts themolten babbitt.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing, wherein preferred embodiments of the present invention areclearly shown.

In the drawing: j

Fig. 1 shows a partial fragmentary view of an apparatus wherein theresistance heating is used to preheat the strip;

Fig. 2 is a modification of the throat design shown in Fig. 1; and

Fig. 3 is still another modification of the throat design as shown inFig. 1.

Referring particularly to Fig. 1, a steel strip 20 is shown which is tobe conditioned so that it may be babbitted with a predeterminedthickness of babbitt on the top side only thereof. The strip 20 passesthrough a pair of spring pressed pinch rolls 22 and :24 which aremounted on` a fixture 26, which is insulated from a support 28 byinsulation 38. The strip then passes beneath a hood 32 supplied withreducing gas through tube 3d and next passes under an extension 36 of ababbitt tank 38 which contains molten babbitt 40 therein. The babbitt 48flows into the extension 36 through one or more orices 42 in the wall oftank `38. The strip 2! then passes into the babbitt tank 38 through athroat portion Ml. Preferably a reducing atmosphere is maintained overthe babbitt 40 to prevent oxidation thereof and this atmosphere may bebled into the extension -36 through an orice E6. Electrical current issupplied to the hook-up by means of connections 48 and 5U. Connection 48is bolted to iixture 26 whereby current passes through the pinch rolls22 and 24. Connection 58 is bolted to babbitt tank 38 wherein thecurrent :flows through the babbitt and into the strip 28 to complete thecircuit. It is apparent from this setup that the current will heat thestrip in accordance with the resistance of the strip between the pointsnoted by arrows A and B since the current passes through the moltenbabbitt 48 contained in the extension 36. In this manner the currententers or leaves the top side of the strip so that the strip between thepinch rolls and the extension only is heated due to the resistancethereof. This heated portion of the strip being beneath said hood 32 issuitably iiuxed by the gas as described in my copending application.

It will be apparent that as the strip 28 moves, it is progressivelyheated,vfluxed and passed into the babbitt tank whereupon the babbittwets the upper surface of the strip which has been cleaned after whichthe strip passes out of the tank through a suitable casting head, notshown, and is cast on to the surface of any desired thickness. stripdoes not pick up any dized by the atmosphere thereof.

Fig. 2 shows a modication of the design shown in Fig. 1 wherein ababbitt tank throat 4:8 is

The backside of the babbitt since itis oxiduring the heating of thestrip in a layer chamfered as at 60 to -form a very thin edge on thebottom side of the throat. In this manner the resistance of the throatat the bottom side thereof is sufficiently great to provide for currentflow through the top side of the strip as it passes into the babbtt.This modiication provides satisfactory results in most cases andeliminates the past difficulties wherein the backside of the strip attimes became wetted with the babbitt.

Fig. 3 shows still another modication which has proved to be highlysatisfactory both from an operation and a design angle. In this instancethe throat 49 is chamfered from opposite sides thereof whereby thebottom portion of the throat does not contact the strip until after ithas passed through the babbitt 40 held in the top portion of the throat,It will be further noted that the outer wall of tank 38 on the upperhalf of the throat extends slightly past the outer portion of the wallat the lower end of the throat and therefore babbitt is actually incontact with the top surface of the strip prior toany lcontact of thestrip with the bottom Portion of the throat. In this manner themodification shown in Fig. 3 is in many respects quite similar to thedesignv shown in Fig, l but more compactly designed, thereby making forgreater simplicity and eliminating difficulties when it is desired tochange the throats 44, such as is necessary when varying Widths of thestrips are desired to be run through the machine. f

In all of the embodiments of invention the prime purpose in mind is tocause the current to flow entirely through the babbitt into the stripwhereby uniform heating of the strip is accomplished. In all of theembodiments a body of the molten babbitt is maintained over the stripprior to any contact of the bottom of the stripl with the babbitt or thethroat. This is to assureA that the current will first pass through thebabbitt into the strip at the top side thereof, thereby eliminating anychance of babbitting of the strip on the bottom side thereof Itisapparent th t other lized but in all cases the same general character-Yisticsv must be maintained in order to accomplish Vthe desired results.

7 From the foregoing it is manifest that I have provided a new throatdesignv which eliminates the possibility of babbitting the backside ofthe strip when heating the strip by resistance heating. It is also to beunderstood that While babbiting operations have been referred to hereinthat any other metal may be cast on the surface of a strip of anysuitable material by the same procedure. For example, steel strip may betinned or overlaid with bronze, aluminum or brass, or nickel, copper,bronze, aluminum strip, etc., may have any suitable lower melting pointalloy or metal cast thereon, in ali cases the procedure being similar tothe procedure referred to herein.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsdesigns may be utimight be adopted, all coming within the scope of 'theclaims which follow.

What is claimed is as follows:

l. In a method of continuously and progressively electrically heatingand simultaneously iiuxing the surface of a strip of metal forsubsequent babbitting operations, the steps comprising: continuouslypassing strip material into a tank'of molten babbitt, progressivelyheating a portion of said strip material by passing current through saidstrip material, from a point sufficiently remote from said tank to yieldthe desired resistance iigure, into the babbitt in said tank whereby thestrip is heated by the resistance thereof While simultaneously providinga reducing gas adjacent the upper surface of said heated strip, andcontinuously maintaining a relatively small body of the babbitt ofsufficient volume and of suiiciently low resistance in contact with thetop side only of the strip to assure passage of current through thebabbitt into vthe strip prior to the entry of the strip into the mainportion of the babbitt in said tank.

2. In an apparatus for continuously .conditiona ing the surface ofmetallic strip material for subsequent application of another metalthereon comprising in combination; a tank for containing molten metal tobe applied, means for acting as one electrode of an electrical circuitin Contact with the strip at a point remote lfrom said tank, and acontainer for molten metal connected to said tank so that molten metalin said container will be in contact with..one surface only of saidstrip prior to the entry of the strip into the tank containing moltenmetal, said container being connected .to the other side of saidelectrical circuit whereby current passing through the strip from saidmeans to said molten metal in said container, heats the strip to thedesired temperature.

3. In a method for continuously and progressively electrically heatingand simultaneously conditioning the surface of a strip of metal forsubsequent casting thereon of another metal the steps comprising:continuously passing strip material into a tank containing said othermetal in the molten state, progressively heating a portion of said stripmaterial prior to its entry into the molten metal by passing an electriccurrent through the said strip material at a point suiciently remotefrom said tank to yield the desired resistance figure, into said moltenmetal, simultaneously providing a reducing atmosphere adjacent onesurface only of the heated portion of said strip, and continuouslymaintaining a body of molten metal of sufiicient volume to permitpassage of the desired current therethrough in contact with said onesurface only of the strip and in a position ahead of the molten metalcontained in said tank wherebythe molten metal contacts the strip on onesurface only thereof to form an electrical circuit therethrough prior tothe contacting of the other surface of the strip with the molten metal.

CECIL A, MANN.

